Ground shaking during a magnitude 7.8 earthquake on the southern San Andreas fault; red indicates areas of strongest ground shaking.

The 2008 Great Southern California ShakeOut was based on a potential magnitude 7.8 earthquake on the southern San Andreas Fault— approximately 5,000 times larger than the magnitude 5.4 earthquake that shook southern California on July 29, 2008. It’s not a matter of if an earthquake of this size will happen—but when. And it is possible that it will happen in our lifetime.

Dr. Lucy Jones of the U.S. Geological Survey led a group of over 300 scientists, engineers, and others to study the likely consequences of this potential earthquake in great detail. The result is the ShakeOut Earthquake Scenario, which was also the basis of a statewide emergency response exercise, Golden Guardian 2008.

In an earthquake of this size, the shaking will last for nearly two minutes. The strongest shaking will occur near the fault (in the projected earthquake, the Coachella Valley, Inland Empire and Antelope Valley). Pockets of strong shaking will form away from the fault where sediments trap the waves (in the projected earthquake, it would occur in the San Gabriel Valley and in East Los Angeles).

Such an earthquake will cause unprecedented damage to Southern California—greatly dwarfing the massive damage that occurred in Northridge’s 6.7-magnitude earthquake in 1994. In summary, the ShakeOut Scenario estimates this earthquake will cause over 1,800 deaths, 50,000 injuries, $200 billion in damage and other losses, and severe, long-lasting disruption. The report has regional implications and is a dramatic call to action for preparedness.

Unless we take action today, there will be major losses of life and property. The ShakeOut has been organized to help raise awareness as well as help Californians prepare for the big earthquakes in our future.

Take the first step in your preparation today— register for the Great California ShakeOut.